Catalytic depolymerisation of polymeric materials

ABSTRACT

A process for converting a molten polymeric material is provided. The process includes effecting disposition of a molten polymeric material, having at least one carbon-carbon double bond, in sufficient proximity to a catalyst material within a reaction zone, to affect a reactive process that effects generation of a reaction product. The reactive process effects cleaving of at least one carbon-carbon double bond. The catalyst material includes [Fe—Cu—Mo—P]/Al 2 O 3  prepared by binding a ferrous-copper complex to an alumina support to generate an intermediate material and reacting the intermediate material with a heteropolyacid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority from U.S.patent application Ser. No. 17/073,277 filed on Oct. 16, 2020, entitled“Catalytic Depolymerisation of Polymeric Materials”.

The '277 was a continuation of U.S. patent application Ser. No.16/576,805 filed on Sep. 20, 2019, also entitled “CatalyticDepolymerisation of Polymeric Materials”.

The '805 was a continuation of U.S. patent application Ser. No.16/000,590 (now U.S. Pat. No. 10,457,886) filed on Jun. 5, 2018 andentitled “Catalytic Depolymerisation of Polymeric Materials”.

The '590 application was a continuation of and claimed priority fromU.S. patent application Ser. No. 14/761,779 (now U.S. Pat. No.10,000,715) filed on Jul. 17, 2015, entitled “Catalytic Depolymerisationof Polymeric Materials.”

The '779 application was a national phase filing of internationalapplication No. PCT/CA2013/000041, filed on Jan. 17, 2013.

The present application also claims priority benefits from the '805,'590, '779 and '041 applications. The '277, '805, '590, '779 and '041applications are hereby incorporated by reference herein in theirentireties.

FIELD OF THE INVENTION

The present disclosure relates to catalyzed depolymerization ofpolymeric materials.

Manufacturers of mechanical equipment, food packagers, and other usersof wax and grease for lubricating, sealing, and other uses have acontinuing need for wax and grease compositions. Manufacturing of thesewaxes and greases are usually expensive. This may be typically due torequirement of pricey petroleum feed in such manufacturing process.

Waxes and grease (or grease base-stocks), in general, are made frompetroleum feed or gas-to-liquid processes. The price of petroleum feedstocks is increasing with time and thus there is a steady increase inprices of waxes and greases. Recently, there have been severaldiscoveries of gas (mostly methane) reservoirs and using aFischer-Tropsch process, these can be converted into higher chain lengthhydrocarbons to give gasoline, lubricating oils, grease base stocks, andwaxes. The products produced this way are relatively more expensive andthus there is a need to utilize readily available polyethylene waste andrecycle them to produce the same materials at considerably lower cost.

It would be advantageous to have a relatively inexpensive process forproducing wax and grease base stock. Such a process would ideallyutilize a readily available inexpensive feedstock and would use aninexpensive process. Waste plastics/polymers have been used in knownprocesses for the manufacture of such products. Plastic waste is amongthe fastest growing solid waste and utilizing this solid waste toproduce useful wax and grease addresses growing plastic disposalproblems

In recent times, there have been considerable efforts to convert thesepolymeric solid wastes into useful products such as fuels, lubricants,waxes and grease base stocks. Existing conversion processes may not beefficient enough and can release green-house gases into the environment.Further, current techniques may be sensitive to quality and quantity ofwaste plastic feed and they can have an impact to the end productquality. This can be especially important as plastic waste can vary inits consistency due to the varying plastic grades.

SUMMARY OF THE INVENTION

In one aspect, there is provided a process for converting a moltenpolymeric material. The process includes effecting disposition of amolten polymeric material, having at least one carbon-carbon doublebond, in sufficient proximity to a catalyst material within a reactionzone, to affect a reactive process that effects generation of a reactionproduct. The reactive process effects cleaving of at least onecarbon-carbon double bond. The catalyst material includes[Fe—Cu—Mo—P]/Al₂O₃ prepared by binding a ferrous-copper complex to analumina support to generate an intermediate material, and reacting theintermediate material with a heteropolyacid.

In another aspect, there is provided a process for converting polymericmaterial to make waxes and grease base stock through catalyticdepolymerisation, comprising: preheating the polymeric material to forma molten polymeric material; starting depolymerisation reaction of themolten polymeric material using a catalyst material in a high-pressurereactor at a desired temperature in the range of 300° C. to 600° C.using heaters in the high-pressure reactor; allowing progression of thedepolymerisation reaction of the molten polymeric material to continueuntil a pressure in the high-pressure reactor reaches a predeterminedvalue in the range of 50 psig to 350 psig; and turning off the heatersand stopping the depolymerisation reaction of the molten polymericmaterial upon the pressure in the reactor reaching the desired value andwherein the polymeric material is converted to wax or a grease basestock; wherein the catalyst material is [Fe—Cu—Mo—P]/Al₂O₃ prepared bybinding a ferrous-copper complex to an alumina support and reacting itwith a heteropolyacid.

In another aspect, there is provided a process for converting primarygranules of polymeric material to make waxes and grease base stockthrough catalytic depolymerisation, comprising: preheating the primarygranules of polymeric material to form a molten primary granules ofpolymeric material; starting depolymerisation reaction of the moltenprimary granules of polymeric material using a catalyst material in ahigh-pressure reactor at a desired temperature in the range of 300° C.to 600° C. using heaters in the high-pressure reactor; allowingprogression of the depolymerisation reaction of the molten primarygranules of polymeric material to continue until a pressure in thehigh-pressure reactor reaches a predetermined value in the range of 50psig to 350 psig; and turning off the heaters and stopping thedepolymerisation reaction of the molten primary granules of polymericmaterial upon the pressure in the reactor reaching the desired value andwherein the primary granules of polymeric material is converted to waxor grease base stock; wherein the catalyst material is[Fe—Cu—Mo—P]/Al₂O₃ prepared by binding a ferrous-copper complex to analumina support and reacting it with a heteropolyacid.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are described herein with reference to the drawings,wherein:

FIG. 1 shows a flow diagram of an exemplary process for converting mixedpolyethylene waste to produce waxes and grease base stocks throughcatalytic depolymerisation, according to one embodiment;

FIG. 2 shows an exemplary graph of gas chromatography-mass spectrometry(GC-MS) results of microcrystalline wax produced using existingprocesses;

FIG. 3 shows an exemplary graph of GC-MS results of wax obtained fromdepolymerisation of high density polyethylene (HDPE) waste, according toone embodiment;

FIG. 4 shows a graph of differential scanning calorimetric (DSC)analysis of the microcrystalline wax produced using existing processes;

FIG. 5 shows a graph of DSC analysis of the wax obtained from thedepolymerization of the HPDE waste, according to one embodiment;

FIG. 6 shows a graph of log shear versus log viscosity of sample 1 ofthe grease base stock, according to one embodiment;

FIG. 7 shows a graph of log shear versus log viscosity of sample 2 ofthe grease base stock, according to one embodiment;

FIG. 8 shows a block diagram of a device for converting the mixedpolyethylene waste to make waxes and grease base stocks, according toone embodiment;

FIG. 9 shows a graph of DSC analysis of the wax obtained from thedepolymerisation of polypropylene, according to one embodiment; and

FIG. 10 is a table illustrating process conditions for the production ofwax obtained from reacting polypropylene in accordance with anembodiment of the present process.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENT(S)

A method of contacting a polymeric material (such as, for example, wastepolymeric material), having at least one carbon-carbon double bond, witha catalyst, to affect a generation of a reaction product is disclosed.In the following detailed description of the embodiments of the presentsubject matter, reference is made to the accompanying drawings that forma part hereof, and in which are shown by way of illustration specificembodiments in which the present subject matter may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the present subject matter, and it is to beunderstood that other embodiments may be utilized and that changes maybe made without departing from the scope of the present subject matter.The following detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present subject matter is definedby the appended claims.

More specifically, there is provided a process of effecting dispositionof a molten polymeric material, having at least one carbon-carbon doublebond, in sufficient proximity to a catalyst material within a reactionzone, to affect a reactive process that effect generation of a reactionproduct, wherein the reactive process effects cleaving of at least onecarbon-carbon double bond. The catalyst material includes[Fe—Cu—Mo—P]/Al₂O₃. The catalyst material is prepared in accordance witha process, the process includes binding a ferrous-copper complex to analumina support to generate an intermediate material, and reacting theintermediate material with a heteropolyacid.

Suitable examples of polymeric material include polyethylene,polypropylene, polyethylene terephthalate, ethylene-vinyl acetate,polyphenylene ether, polyvinyl chloride, polystyrene, lignin, nylon, orcellulose. In some embodiments, for example, the polymeric materialincludes any one of, or any combination of, polyethylene, polypropylene,polyethylene terephthalate, ethylene-vinyl acetate, polyphenylene ether,polyvinyl chloride, polystyrene, lignin, nylon, or cellulose.

In some embodiments, for example, and as mentioned above, the polymericmaterial includes waste polymeric material. Suitable waste polymericmaterial includes mixed polyethylene waste, mixed polypropylene waste,and a mixture including mixed polyethylene waste and mixed polypropylenewaste. The mixed polyethylene waste can include low density polyethylene(LDPE), linear low density polyethylene (LLDPE), high densitypolyethylene (HDPE), polypropylene (PP), or a mixture including anycombination of LDPE, LLDPE, HDPE, and PP. In some embodiments, forexample, the mixed polyethylene waste includes grocery bags, milkpouches, stationery files. In some embodiments, for example, the wastepolymeric material feed includes up to 10 weight % of material that isother than polymeric material, based on the total weight of the wastepolymeric material.

In some embodiments, for example, the polymeric material includesprimary granules of a polymeric resin.

In some embodiments, for example, the process is affected within areaction vessel. Depending on the nature of the polymeric material, thewall temperature of the vessel should, preferably, not exceed a maximumtemperature. If the wall temperature is excessive, thermal degradationof the resin will be affected on the internal wall surface of thevessel, and the reaction may proceed in an uncontrollable fashion. Aswell, the process may, generally, be unable to affect the desiredselectivity, and also be unable to achieve desirable yields of thedesired product material, such that excessive greases, oils and gasesare present in the product material.

In some embodiments, for example, if the polymeric material includespolymers with functional groups containing aromatics, halogens,nitrogen, oxygen, or sulphur, the vessel and all process piping arefabricated from either 316 stainless steel or Hastelloy™, or areglass-lined to avoid degradation of the steel by acidic or highlyreactive side products.

In some embodiments, for example, appropriate venting procedures andcontainment units are provided for removal of any aromatics, volatileorganic compounds, or acidic vapour (e.g. HCI) that is present in theheadspace of the reaction vessel during depolymerisation. Furtherprocessing through distillation, solvent washes, or use of variousabsorbent materials will allow for removal of remaining trace acidic,coloured, or aromatic compounds in the wax.

In those embodiments where the polymeric material is difficult to meltor isolate in a free-flowing liquid form (e.g. lignin), in some of theseembodiments, for example, an appropriate solvent or ionic liquid isemployed to dissolve the provided polymeric material prior to havingdecomposition effected in the presence of the catalyst material.

In some embodiments, for example, the reactive process is affected in areaction zone of the reaction vessel. In some of these embodiments, forexample, the pressure within the reaction zone is within the range of 10to 10,000 psig, the temperature within the reaction zone is within therange of 250 to 500 degrees Celsius, the vessel wall temperature iswithin the range of 300 to 700 degrees Celsius, the amount of catalystmaterial present within the reaction zone is within the range of 0.5 to10 weight %, based on the total weight of the mixture of the polymericmaterial and the catalyst material, the volume of the mixture of thepolymeric material and the catalyst material defines 70% of the totalavailable space within the reaction vessel, and the headspace within thereaction vessel includes air or nitrogen, or may be defined by a vacuum,or substantially a vacuum.

For polyethylene, polyethylene waste, or mixed polyethylene waste, thetemperature within the reaction zone is within the range of 300 to 600degrees Celsius, and the pressure within the reaction zone is within therange of 50 psig to 350 psig.

In some embodiments, for example, the process effects depolymerisationof at least a fraction of the polymeric material. The process requiresmuch lower energy than other known depolymerisation processes, andallows for selective production of synthetic waxes, greases, oil orsolvents, with yields of, potentially, greater than 90%. When asynthetic wax is targeted with a yield of 90 to 99%, this is achievedwith a one (1) to nine (9) % hydrocarbon oil product.

In some embodiments, for example, wax generated through this process hasmelting points in the range of 75 to 170 degrees Celsius. Variation inthe melting points is achieved by varying pressure within the reactionzone, temperature within the reaction zone, and the source resin.

In some embodiments, for example, the process further includes, whilethe molten polymeric material is disposed in sufficient proximity to thecatalyst material within a reaction zone to effect a reactive processthat effects generation of a reaction product, wherein the reactiveprocess effects cleaving of at least one carbon-carbon double bond,heating the reaction zone such that the reaction zone is disposed at atemperature that is effective for the effecting of the reactive process,and suspending the heating when the pressure within the reaction zonebecomes disposed at a predetermined pressure. The predetermined pressureis correlated with the existence of a desirable reaction product. As thereactive process is affected, pressure increases. This is because thereactive process effects production of lower molecular weight materials,which typically have lower vapour pressure, and which, therefore, have agreater tendency to be disposed in the gaseous phase. The disposition ofthe reaction zone at the predetermined pressure is an indication thatthe reactive process has proceeded such that generation of a desirablereaction product has been affected. The predetermined pressure is basedon the reaction product whose generation is desired to be affected fromthe reactive process, and may vary, depending on the desired reactionproduct. In some embodiments, for example, the predetermined pressurecan be varied to effect generation of different grades of waxes andgrease base stocks. For polyethylene, polyethylene waste, or mixedpolyethylene waste, the predetermined pressure is within the range of 50psig to 350 psig. For polypropylene, the predetermined pressure iswithin the range of 50 psig to 1000 psig.

In some embodiments, for example, the polymeric material is pre-heatedwithin an extruder so as to effect generation of the molten polymericmaterial, and the molten polymeric material is then supplied to thereaction vessel by motive forces applied by the extruder to thepolymeric material. In some embodiments, for example, the extrudereffects substantially continuous pushing of the molten polymericmaterial into the reaction vessel.

In some embodiments, for example, the reaction product collects at thebottom of the reaction vessel. In this respect, in some of theseembodiments, for example, the reaction product is drained from thereaction vessel (such as, for example, into a container).

In some embodiments, for example, the process further includes, afterthe draining of the reaction product into a container, inducingcoalescence of pigments, particles, and other impurities, within thedrained reaction product, using a high to low pressure cycle, andallowing the pigment, particles and other impurities to settle out fromthe reaction product such that separate phases are generated.

The following is a discussion of exemplary embodiments of the process,including practising of the process with specific examples of polymericmaterial.

(a) Mixed Polyethylene Waste

FIG. 1 shows a flow diagram 100 of an exemplary process for producingwaxes and grease base stocks through catalytic depolymerization of mixedpolyethylene waste, according to one embodiment. Waxes are slipperysolid materials that are easy to melt. Generally, the melting point ofwaxes ranges between 45° C. to 130° C. and flash point (i.e. lowesttemperature at which the wax can vaporize to form an ignitable mixturein air) ranges between 180° C. to 350° C. The waxes may be mostlyderived by refining crude petroleum. The waxes may be also derived fromnatural secretions of plants and animals. Further, the waxes may besynthetically produced using processes such as Fischer-Tropsch.

The grease or grease base stock is a semi-solid substance introducedbetween two moving surfaces to reduce the friction between them,improving efficiency and reducing wear. Commercially available greasesare generally made by mixing grease base stocks with small amounts ofspecific additives to give them desired physical properties. Generally,greases are of four types: (a) admixture of mineral oils and solidlubricants (b) blends of residuum, waxes, uncombined fats, rosin oilsand pitches, (c) soap thickened mineral oils and (d) synthetic greaseslike poly-alpha olefins, silicones, etc.

The mixed polyethylene waste may include LPDE, LLPDE, or HPDE, or anycombination thereof. For example, the polyethylene waste may beavailable as shopping bags, grocery bags as sacks of HDPE, milk pouchesof LDPE and stationery files of LLDPE. In one embodiment, primarygranules of polyethylene may be also used for producing the waxes andgrease base stocks. Further, the mixed polyethylene waste may includeimpurities (e.g., such as polypropylene and polystyrene) up to about10%.

At step 102, the mixed polyethylene waste is preheated to form a moltenmixed polyethylene waste. For example, the mixed polyethylene waste ispreheated in an extruder attached to a high-pressure reactor (e.g., thereactor 804 of FIG. 8). The molten mixed polyethylene waste formed inthe extruder is substantially continuously pushed into the high-pressurereactor. At step 104, depolymerisation reaction of the molten mixedpolyethylene waste is started using a catalyst in the high-pressurereactor at a desired temperature using heaters in the high-pressurereactor. The catalyst used is [Fe—Cu—Mo—P]/Al₂O₃ which is disposed on astirring blade of the high-pressure reactor. The catalyst is prepared bybinding a ferrous-copper complex to an alumina support and reacting itwith a heteropolyacid to obtain the final catalyst. The temperature inthe high-pressure reactor is in the range of about 300° C. to 600° C.

At step 106, progression of the depolymerisation reaction of the moltenmixed polyethylene waste is allowed to continue until a pressure in thehigh-pressure reactor reaches a desired value. The pressure in thehigh-pressure reactor is in the range of about 50 psig-350 psig. At step108, the desired value of the pressure in the high-pressure reactor isvaried to produce different grades of waxes and grease base stocks. Forexample, the different grades of waxes include waxes having differentmelting points ranging from 60° C. to 100° C.

At step 110, the heaters are turned off and the depolymerisationreaction of the molten mixed polyethylene waste is stopped upon thepressure in the reactor reaching the desired value. During thedepolymerisation reaction, the molten mixed polyethylene waste isconverted to wax or grease base stock. At step 112, the converted wax orthe grease base stock is drained into a container when the converted waxor the grease base stock is liquid and is substantially above flashpoint.

It can be noted that, during the depolymerisation reaction, there is nogas liberated and thus, there is a complete carbon recovery in the formof waxes or grease base stocks. At step 114, coalescence of pigmentparticles/impurities in the drained converted wax or the grease basestock is started using a high to low pressure cycle. At step 116, thepigment particles/impurities and the converted wax or grease base stockare allowed to settle in the container as separate layers.

FIG. 2 shows, in the context of the invention, an exemplary graph 200 ofgas chromatography-mass spectrometry (GC-MS) results of microcrystallinewax produced using existing processes. For example, GC-MS is a methodthat combines features of gas liquid chromatography and massspectrometry to identify different components in the microcrystallinewax produced using existing processes. (The microcrystalline waxes aretype of waxes that have melting points ranging from 60° C. to 100° C.and are generally harder than paraffin waxes). The x-axis of the graph200 represents retention time and y-axis represents intensity.

FIG. 3 shows an exemplary graph 300 of GC-MS results of wax obtainedfrom depolymerisation of high density polyethylene (HDPE) waste,according to one embodiment. The depolymerisation reaction of the HOPEwaste is performed according to the process explained in FIG. 1. About3.5 kg of the HOPE waste purchased from local market is taken for thedepolymerisation reaction in the high-pressure reactor (which has acapacity of 6.5 liters). Different experiments are carried out tocompare properties of the wax obtained from the depolymerisationreaction with that of the microcrystalline wax produced using theexisting processes.

In Experiment 1, a desired pressure of 140 pound-force per square inchgauge (psig) is chosen. When the pressure inside the high-pressurereactor reaches 140 psig, the depolymerisation reaction is stopped. Thewax obtained is drained, cooled, and tested for GC-MS. TABLE 1 showsproperties of the wax obtained through the depolymerisation reactioncompared against commercially available ARGE wax (a type ofFischer-Tropsch wax).

TABLE 1 Wax obtained Commercial by catalytic ARGE depolymerization SI.No. Properties wax of HDPE waste 1 Melting Point (° C.) 105 97 2 AverageNumber of 47 48 Carbons 3 Nuclear magnetic Identical Identical resonance(NMR) 4 Solubility in Acetone 28 17.5 (weight %) 5 Solubility inCyclohexane 69 75 (wt %) 6 IR Identical Identical 7 Acid value 0 0 8Saponification No. 0 0

The graph 200 and the graph 300 are compared. The comparison ofmolecular weight distribution (MWD) is shown in TABLE 2.

TABLE 2 Microcrystalline Was obtained by wax produced catalytic SI. Testusing existing depolymerization No. Properties method processes of HDPEwaste 1 Melting Point (° C.) Differential 67.84 72.42 scanningcalorimetry (DSC) 2 Structural GC-MS C₂₀-C₃₉ C₁₄-C₄₁ information

It can be inferred from TABLE 2 and the graphs 200 and 300 that, the waxobtained from the depolymerization of the HDPE waste has broader MWD andslightly higher melting point but is otherwise comparable to themicrocrystalline wax produced using the existing processes.

FIG. 4 shows, in the context of the invention, a graph 400 ofdifferential scanning calorimetric (DSC) analysis of themicrocrystalline wax produced using existing processes. DSC is athermoanalytical technique in which difference in amount of heatrequired to increase temperature of a sample and reference is measuredas a function of temperature. The x-axis of the graph 400 representstemperature and the y-axis represents heat flow.

FIG. 5 shows a graph 500 of DSC analysis of the wax obtained from thedepolymerization of HPDE waste, according to one embodiment. The graph400 and the graph 500 are compared. The melting point of the waxobtained from the depolymerization of the HDPE is about 10% higher thanthat of the microcrystalline wax produced using the existing processes.Further, the wax produced from the HDPE is found to have a natural tackwhich makes it highly suitable for wax polishes and shoe polishes.

Experiment 2 considers the melting point of wax which is an importantproperty. The melting point of wax is determined by the desired value ofpressure inside the high-pressure reactor. TABLE 3 below shows differentvalues of pressure which yields waxes of different melting points.

TABLE 3 SI. No. Pressure (psig) Melting point of product wax (° C.) 1 50100 2 80 90 3 110 80 4 140 75 5 200 60

In Experiment 3, the following composition of feed is considered in thehigh-pressure reactor. It should be noted that the HDPE, LDPE, and LLDPEare available as primary granules.

1. Primary granules of HDPE, LDPE and LLDPE as pure feed

2. Waste materials of HDPE, LDPE and LLDPE as pure feed

3. Various mixtures of primary granules of HDPE, LDPE and LLDPE

4. Various mixtures of waste materials of HDPE, LDPE and LLDPE

5. Mixture of (1) and (2)

6. Waste materials of HDPE, LDPE and LLDPE as pure feeds with 10% ofimpurities of polystyrene and polypropylene.

In each of the cases, the desired value of pressure inside thehigh-pressure reactor remained unchanged indicating that the catalyst isspecific to breaking of CH₂—CH₂ bonds and is relatively insensitive tothe nature of feed.

In Experiment 4, water emulsion of various waxes produced in Experiment2 is prepared and below composition is followed:

Composition A—Wax 5 g and Stearic acid 2.5 g

Composition B—Water 300 g, Morpholine 3 g and Stearic acid 2.5 g

Solids in composition A are mixed and melted. This is mixed with alreadyheated composition B. The emulsion is obtained on stirring. It can beseen that, the emulsion is stable and the wax does not separate from thewater layer. The emulsion thus formed forms a very thin layer of wax oncoating having strength depending upon the melting point of the waxused.

In Experiment 5, grease base stock is produced for cut-off pressure of250-300 psig (which is Sample 1) and cut-off pressure of 300-350 psig(Sample 2). In one embodiment, viscosities of the sample 1 and thesample 2 are determined as a function of temperature and shear rate.

FIG. 6 shows a graph 600 of log shear versus log viscosity of sample 1of the grease base stock, according to one embodiment. The log shear isrepresented on x-axis and log viscosity is represented on y-axis of thegraph 600. The shear rate, shear stress and viscosity of sample 1 at 40°C., 100° C. and 150° C. are given in TABLES 4, 5 and 6.

TABLE 4 (at 40° C.) Shear Rate [1/s] Shear Stress [Pa] Viscosity [Pa ·s] 0.01 18.9 1,890 0.0147 16.8 1,150 0.0215 16.9 786 0.0316 17.9 5660.0464 19 410 0.0681 20.5 301 0.1 22.7 227 0.147 25.7 175 0.215 29.6 1370.316 34.6 110 0.464 41.8 90 0.681 52.9 77.7 1 70.8 70.8 1.47 92.3 62.92.15 106 49.2 3.16 112 35.5 4.64 117 25.2 6.81 122 17.9 10 128 12.8 14.7135 9.22 21.5 145 6.72 31.6 156 4.94 46.4 172 3.71 68.1 193 2.83 100 2192.19

TABLE 5 (at 100° C.) Shear Rate [1/s] Shear Stress [Pa] Viscosity [Pa ·s] 0.464 0.00276 0.00594 0.681 0.019 0.0278 1 0.0285 0.0285 1.47 0.06690.0456 2.15 0.0835 0.0388 3.16 0.0983 0.0311 4.64 0.0751 0.0162 6.810.148 0.0217 10 0.157 0.0157 14.7 0.238 0.0162 21.5 0.312 0.0145 31.60.441 0.0139 46.4 0.613 0.0132 68.1 0.85 0.0125 100 1.2 0.012

TABLE 6 (150° C.) Shear Rate [1/s] Shear Stress [Pa] Viscosity [Pa · s]0.01 0.00319 0.319 0.0147 0.00233 0.159 0.0215 0.00202 0.0939 0.03160.00055 0.0175 0.0464 0.000423 0.00912 0.0681 0.00258 0.0379 0.1 0.002650.0265 0.147 0.00532 0.0363 0.215 0.00772 0.0358 0.316 0.0155 0.04910.464 0.0215 0.0464 0.681 0.0295 0.0432 1 0.0374 0.0374 1.47 0.04180.0285 2.15 0.0407 0.0189 3.16 0.0574 0.0181 4.64 0.0637 0.0137 6.810.0835 0.0123 10 0.104 0.0104 14.7 0.136 0.00924 21.5 0.167 0.00777 31.60.214 0.00677 46.4 0.285 0.00614 68.1 0.426 0.00625 100 0.583 0.00583

FIG. 7 shows a graph 700 of log shear versus log viscosity of sample 2of the grease base stock, according to one embodiment. The log shear isrepresented on x-axis and log viscosity is represented on y-axis of thegraph 700. The shear rate, shear stress and viscosity of sample 1 at 40°C., 100° C. and 150° C. are given in TABLES 6, 7 and 8.

TABLE 6 (40° C.) Shear Rate [1/s] Shear Stress [Pa] Viscosity [Pa · s]0.00998 617 61,800 0.0147 632 43,000 0.0215 657 30,500 0.0316 693 21,9000.0464 736 15,900 0.0681 798 11,700 0.1 879 8,790 0.147 987 6,720 0.2151,130 5,240 0.316 1,300 4,120 0.464 1,470 3,170 0.681 1,520 2,230 11,520 1,510 1.47 1,470 1,000 2.15 1,530 709 3.16 1,720 544 4.64 1,820393 6.81 2,280 335 10 3,170 316 14.7 3,290 224 21.6 3,070 142 31.6 3,10097.9 46.4 2,880 62.1 68.1 2,840 41.7 100 2,760 27.6

TABLE 7 (at 100° C.) Shear Rate [1/s] Shear Stress [Pa] Viscosity [Pa ·s] 0.00999 175 17,500 0.0147 38.5 2,630 0.0215 39 1,810 0.0316 40.11,270 0.0464 44.1 950 0.0681 43.9 644 0.1 45.8 458 0.147 48.1 328 0.21551.3 238 0.316 53.8 170 0.464 55.4 119 0.681 60.9 89.4 1 69.5 69.5 1.4776.8 52.3 2.15 83.5 38.8 3.16 84.6 26.8 4.64 82.8 17.8 6.81 74.8 11 1059.2 5.92 14.7 53.9 3.67 21.5 45.7 2.12 31.5 110 3.49 46.4 40.2 0.86768.1 50.7 0.744 100 45.8 0.458

TABLE 8 (at 150° C.) Shear Rate [1/s] Shear Stress [Pa] Viscosity [Pa ·s] 0.01 11.6 1,160 0.0147 9.23 628 0.0316 5.77 183 0.0464 5.59 1200.0681 4.54 66.7 0.1 4.48 44.8 0.147 4.46 30.4 0.215 4.46 20.7 0.3164.61 14.6 0.464 3.86 8.32 0.681 3.9 5.72 1 3.97 3.97 1.47 4.08 2.78 2.153.63 1.69 3.16 3.72 1.18 4.64 3.6 0.776 6.81 3.55 0.521 10 3.92 0.39214.7 4.04 0.275 21.5 3.72 0.173 31.6 4.41 0.14 46.4 5.82 0.125 68.1 7.260.107 100 10 0.1

The above-mentioned experiments suggest that smaller cut-off pressureyields grease base stocks with higher viscosity. As the temperature ofthe grease base stock is increased, value of the viscosity is decreasedas expected. For a given temperature and cut-off pressure, the viscosityis dependent upon the shear rate and falls drastically. Up to 100 persecond shear rate, the viscosity falls by a factor of 1000, leading toan increase in lubrication by the same factor. This indicates that thegrease base stock has a natural ability to give a high degree oflubrication.

FIG. 8 shows a block diagram 800 of a device for producing waxes andgrease base stocks through catalytic depolymerisation of waste plastics,according to one embodiment. Particularly, the device includes anextruder 802, a furnace 830, a reactor 804, a condenser 806, a drum 808,a drum 810, and a tray 828.

The extruder 802 is a four-inch barrel which is twenty-four inches long.The extruder 802 preheats the polyethylene waste and pushes moltenpolyethylene waste to the reactor 804. The extruder 802 operates at 300°C. and pushes the molten polyethylene waste through a valve 816. In oneembodiment, preheating the polyethylene waste may make possible lowerprocessing time of the polyethylene waste in the reactor 804 since thepreheating takes place outside the reactor 804 (in the extruder 802).Further, a semicontinuous process is ensured in the reactor 804.

The reactor 804 is 2 cm thick, 15 cm in diameter and 30 cm in length andhas a working capacity of 6.5 liters. As shown, the furnace 830 includesheaters 812 to heat the reactor 804. The temperature in the reactor 804is maintained at 450° C. The reactor 804 includes a stirrer 814, apressure gauge 822, and a catalyst bucket 824. The reactor 804 isdesigned in such a way that walls of the reactor 804 withstands hightemperature and pressures during the depolymerisation process. Thecatalytic bucket 824 carries a catalyst which accelerates thedepolymerisation reaction of the molten polyethylene waste in thereactor 804. In one example embodiment, the catalyst used is[Fe—Cu—Mo—P]/Al₂O₃.

In operation, when the reactor 804 receives the molten polyethylenewaste, the temperature falls from 450° C. When the temperature falls,temperature of the heaters 812 is increased to ensure that pressureinside the reactor 804 is maintained at one atmospheric pressure byclosing a valve 818 and opening a valve 820. The pressure inside thereactor 804 is measured using the pressure gauge 822. In one embodiment,the pressure inside the reactor 804 affects quality of wax formed. Itcan be noted that, volume of the molten polyethylene waste which is fedinto the reactor 804 is doubled at the temperature inside the reactor804.

The valve 816 and the valve 820 are closed to increase the pressure inthe reactor 804. When a desired pressure (in the range of 50 psig-350psig) is reached inside the reactor 804, the heaters 812 are turned offand the depolymerisation reaction is stopped. The depolymerisationreaction takes about one hour in the reactor 804. The valve 820 isgradually opened and the pressure inside the reactor 804 is allowed tofall to one atmospheric pressure. Vapor from the reactor 804 escapesthrough the valve 820 to the condenser 806 and is finally collected inthe drum 808. The temperature inside the reactor 804 remains unchanged.

As the pressure in the reactor 804 falls to one atmospheric pressure,the valve 820 is closed and the valve 818 is opened to drain producedmaterial. The pressure reduction to one atmosphere inside the reactor804 initiates coalescence process of organic and inorganic pigmentimpurities (such as carbon, calcium carbonate, etc.) present along withthe polyethylene waste. The pigment impurities coalesce and settle asseparate layers through manipulation of the valves 816, 818 and 820.There is no requirement of an additional process to separate the pigmentimpurities from the produced waxes and grease base stocks. Thus, high tolow pressure cycles inside the reactor 804 separates the pigmentimpurities leaving behind pure waxes and grease base stocks. The slightamount of pressure that is developed inside the reactor 804 pushes theproduced products from the reactor 804 into the drum 810.

When the products are poured into the drum 810 at over 400° C., smallamounts of hydrocarbon vapors may be produced. A pipe 826 over the drum810 ensures that the hydrocarbon vapors so formed do not escape intoatmosphere and is completely condensed within the drum 810. Thishydrocarbon vapors form a protective covering on top of the wax or thegrease base stock preventing the wax and the grease base stocks comingin direct contact with the atmosphere and its burning. The productscollected in the drum 810 are condensed at 200° C. and is then drainedinto the tray 828. This process ensures that the liquid products may bedrained out at over 400° C., even though such a temperature issignificantly above flash point of the waxes or grease base stocks.

The reduction of pressure and removal of the produced material from thereactor 804 may take about 30 minutes. Thus, one cycle of the catalyticdepolymerisation may take about two and a half hours. It can be seenthat, the depolymerisation reaction is not sensitive to impurities suchas polypropylene and polystyrene up to about 10% present along thepolyethylene waste. Waxes and grease base stocks of specified qualitymay be obtained by manipulating process conditions and valves 818 and820. For example, by manipulating the desired pressure inside thereactor 804, waxes of different grades (e.g., having different meltingpoints) are obtained.

In various embodiments, the processes described in FIGS. 1 through 8uses a new catalyst which is not deactivated and lasts for over one yearof use in the process, thereby making the process economical. Thecatalyst is stable throughout the reaction temperatures of 300° C.-600°C. and depolymerizes HDPE, LDPE, and LLDPE equally. The catalyst is alsounaffected by any pigment impurities. Further, the use of extruder forpreheating the polyethylene waste ensures that molten polyethylene wasteat high temperatures is fed into the reactor. This may also enable asemi-continuous process in the reactor. During the above-describedprocess, there is a total carbon recovery of the polyethylene waste intodesired products, which makes the process eco-friendly.

(b) Polypropylene

Batch depolymerisation of polypropylene resin to lower molecular weightfractions occurs within a reaction temperature range of 300 to 400degrees Celsius when one (1) to six (6) weight % of the above-describedcatalyst material. In comparison to other polymeric materials, such asLDPE, LLDPE, and HDPE, undergoes depolymerisation at lower temperatures(generally, 30 to 50 degrees Celsius lower than that for other polymericmaterials).

Depolymerisation of polypropylene, in accordance with the presentprocess, requires lower thermal energy than other processes, and allowsfor selective production of synthetic hydrocarbon waxes, greases, oilsor solvents with yields of greater than 95%. When polypropylene wax istargeted, a yield of 95 to 99% is achieved with 1 to 5 weight %hydrocarbon oil by-product, based on the total weight of the product.Polypropylene wax, generated by the present process, will have adecrease in discoloration and yield a brittle wax (penetration of lessthan one (1) dmm) and melting points as high as 170 degrees Celsius,which is 20 to 30 degrees Celsius higher than polyethylene-based waxesmade through the same process. Variation in the polypropylene waxmelting points is achieved by varying reaction pressure, reactiontemperature, and the melting point of the source resin. In someembodiments, for example, to obtain polypropylene waxes with meltingpoints above 150 degrees Celsius, polypropylene resins with softeningpoints above 150 degrees Celsius could be used.

If the amount of energy applied to the reaction is excessive (the heatapplied to the reaction vessel wall exceeds 500 degrees Celsius), thereaction will proceed in an uncontrollable fashion. As well, the processmay, generally, be unable to affect the desired selectivity, and also beunable to achieve desirable yields of the desired product material, suchthat excessive greases, oils and gases are present in the productmaterial.

In some embodiments, for example, the reactive process is affected in areaction zone of the reaction vessel. In some of these embodiments, forexample, the pressure within the reaction zone is within the range of 10to 10,000 psi, the temperature within the reaction zone is within therange of 300 to 400 degrees Celsius, the vessel wall temperature iswithin the range of 400 to 500 degrees Celsius, the amount of catalystmaterial present within the reaction zone is within the range of 1 to 6weight %, based on the total weight of the mixture of the polymericmaterial and the catalyst material, the volume of the mixture of thepolymeric material and the catalyst material defines 56% of the totalavailable space within the reaction vessel, and the headspace within thereaction vessel includes air or nitrogen, or may be defined by a vacuum,or substantially a vacuum. Also, in some of these embodiments, a mixeris disposed within the reaction zone, and the mixer is operated at aspeed within the range of 45 to 700 rpm. When implementing the process,in accordance with the above-described conditions, a polypropylene waxis produced having a melting point within the range of 100 to 170degrees Celsius, a penetration within the range of 0 to 10 dmm, and aviscosity within the range of 25 to 2000 cps.

FIG. 9 shows a graph of DSC analysis of the wax obtained from thedepolymerisation of polypropylene, according to one embodiment.

FIG. 10 is a table illustrating four separate trials which effectedproduction of wax by reacting polypropylene in accordance with anembodiment of the present process. Each one of the trials were carriedout under different process conditions.

Although the present embodiments have been described with reference tospecific example embodiments, it will be evident that variousmodifications and changes may be made to these embodiments withoutdeparting from the broader spirit and scope of the various embodiments.

What is claimed is:
 1. A wax prepared by a method, said methodcomprising: (a) selecting a waste polymeric feed, (b) heating said wastepolymeric feed to create a molten polymeric material; and (c)depolymerizing said molten material in a reaction vessel until apredetermined pressure is reached to create said wax.
 2. The wax ofclaim 1 wherein said depolymerization is aided by a catalyst.
 3. The waxof claim 2 wherein said catalyst is [Fe—Cu—Mo—P]/Al₂O₃.
 4. The wax ofclaim 1 wherein said waste polymeric feed comprises at least 90%polypropylene.
 5. The wax of claim 4 wherein the temperature in saidreaction vessel is between 300° C. to 400° C. during saiddepolymerization.
 6. The wax of claim 4 wherein the temperature of awall of said reaction vessel does not exceed 500° C.
 7. The wax of claim4 wherein said wax has a melting point between 100 and 170° C.
 8. Thewax of claim 4 wherein said depolymerization is aided by a catalyst,wherein said catalyst is [Fe—Cu—Mo—P]/Al₂O₃.
 9. The wax of claim 8wherein said catalyst is between 1 to 6 percent weight of the totalweight of the mixture of said molten polymeric material and saidcatalyst.
 10. The wax of claim 4 wherein said predetermined pressure iswithin the range of 10 to 10,000 psi.
 11. The wax of claim 1 whereinsaid waste polymeric feed comprises at least 90% polyethylene.
 12. Thewax of claim 11 wherein the temperature in said reaction vessel isbetween 300° C. to 600° C. during said depolymerization.
 13. The wax ofclaim 11 wherein the temperature of a wall of said reaction vessel doesnot exceed 700° C.
 14. The wax of claim 11 wherein said wax has amelting point 45° C. to 130° C.
 15. The wax of claim 11 wherein saiddepolymerization is aided by a catalyst, wherein said catalyst is[Fe—Cu—Mo—P]/Al₂O₃.
 16. The wax of claim 15 wherein said catalyst isbetween 0.5 to 10 percent weight of the total weight of the mixture ofsaid molten polymeric material and said catalyst material.
 17. The waxof claim 11 wherein said predetermined pressure is within the range of50 to 350 psi.
 18. The wax of claim 11 wherein said waste polymeric feedfurther comprises grocery bags, milk pouches, and/or stationery files.19. The wax of claim 1 wherein said waste polymeric feed comprisespolystyrene.
 20. The wax of claim 1 wherein said method furthercomprises: (d) inducing coalescence of an impurity from said wax andallowing said impurity to settle out of said wax.